Rotatable mounting fixture for a lamp



FIG. 1 is a perspective view of a rotatable mounting fixture for a lamp showing my new design;

FIG. 2 is a top plan view thereof;

FIG. 3 is a bottom plan view of a base thereof;

FIG. 4 is a side elevation of thereof with a panel removed; and,

FIG. 5 is a perspective view thereof with the panel removed. 

The ornamental design for a rotatable mounting fixture for a lamp, as shown and described. 